Molten slags include, for example, molten blast furnace slag, molten converter slag, and molten electric furnace slag. It has been known that it is possible to obtain a rapidly cooled solidified slag by cooling a molten slag at a high cooling rate for solidification. The rapidly cooled solidified slag having a high vitrification ratio thus obtained is suitable, for example, as a cement material (extending agent).
FIG. 1 shows an apparatus for manufacturing a rapidly cooled solidified slag, which is partially different from but substantially the same as the apparatus for manufacturing a rapidly cooled solidified slag disclosed in the U.S. Pat. No. 4,050,884 dated Sept. 27, 1977. More specifically, FIG. 1 is a schematic sectional view illustrating an embodiment of the apparatus for manufacturing a rapidly cooled solidified slag. In FIG. 1, 1 is an enclosed-structure housing. The housing 1 has an opening 1a at the top thereof for passing a molten slag, and a discharge port 1b at the lower end thereof for discharging a crushed rapidly cooled solidified slag. In the housing 1, a pair of cooling drums 2 each having the same diameter and the same length are arranged so that the axial directions thereof are parallel to each other in the same horizontal plane. Each of the pair of cooling drums 2 is rotated by a suitable driving means (not shown) in directions opposite to each other at the same peripheral speed, as shown by the arrows "a" and "a'" in FIG. 1, in the rising direction of the peripheral surface of each of the pair of cooling drums 2 at the contact portion thereof. A plurality of cooling through-holes (not shown) are pierced in the peripheral wall of each of the pair of cooling drums 2 in the axial direction thereof. One end of each of the plurality of cooling through-holes communicates with a hollow portion (not shown) of one end of the center axle of the cooling drum 2, and the other end of the cooling through-holes communicates with a hollow portion (not shown) of the other end of the center axle of the cooling drum 2. The hollow portion of the above-mentioned one end of the center axle of the cooling drum 2 is liquid-tightly connected to one end of a pipe 3 through a swivel joint (not shown). An end of another pipe 6 provided with a pump 5 on the way is connected to the outlet of the heat absorbing section of a heat exchanger 4. The other end of the pipe 6 is liquid-tightly connected to the hollow portion of the other end of the center axle of the cooling drum 2 through another swivel joint (not shown). In FIG. 1, one heat exchanger 4 is shown to be connected to one of the cooling drums 2, however, another heat exchanger not shown is also connected to the other one of the cooling drums 2 in the same way as mentioned above. And, a cooling medium for cooling the cooling drum 2 is supplied to the plurality of cooling through-holes of the peripheral wall of the cooling drum 2 through the pipe 6 and the center axle of the cooling drum 2 by means of the pump 5. The cooling medium supplied to the plurality of cooling through-holes is heated as described later by means of the heat contained in the molten slag which is deposited on the peripheral surface of the cooling drum 2, and supplied to the heat absorbing section of the heat exchanger 4 through the center axle of the cooling drums 2 and the pipe 3 while partially generating steam. The cooling medium supplied to the heat absorbing section of the heat exchanger 4 is cooled through heat exchange in the heat exchanger 4 with water supplied to the radiator section thereof. The cooling medium cooled in the heat absorbing section of the heat exchanger 4 is suppled again into the plurality of cooling through-holes in the peripheral wall of the cooling drum 2 through the pupe 6 by means of the pump 5. Thus, the cooling medium circulates through the cooling drum 2 and the heat exchanger 4. On the other hand, the steam obtained in the radiator section of the heat exchanger 4 through heat exchange with the cooling medium flowing in the heat absorbing section of the heat exchanger 4 is fed to the turbine 7 to drive the same, then fed to the condenser 8 to become water, and then supplied again to the radiator section of the heat exchanger 4. In FIG. 1, 9 is an electric power generator driven by the turbine 7, 10 is a cooling tower for cooling the cooling water for the condenser 8, and 11 is a pump for causing the cooling water for the condenser 8 to circulate through the cooling tower 10 and the condenser 8.
As shown in FIG. 1, a pair of weirs 12 are provided in the upper halves of the both ends of each of the pair of cooling drums 2 so as to be in contact with the both ends of each of the pair of cooling drums 2 (FIG. 1 shows only one of the pair of weirs 12). The top ends of each of the pair of weirs are connected to each other by a cover 12' which has an opening 12'a at the center thereof. The pair of weirs 12 and the single cover 12' are supported on the housing 1 by means of a suitable supporting means not shown. A slag sump 13 is formed by the upper half of the peripheral surface of each of the pair of cooling drums 2 in cooperation with the pair of weirs 12. A slag runner 14 for pouring the molten slag 15 into the slag sump 13 is provided above the pair of cooling drums 2. The molten slag 15 from the slag runner 14 is poured through the opening 1a of the housing 1 and the opening 12'a of the cover 12' into the slag sump 13 where a slag pool is formed. The molten slag 15 poured into the slag sump 13 is deposited onto the peripheral surface of each of the pair of cooling drums 2 during rotation thereof, and the molten slag 15 deposited on the peripheral surface of each of the pair of cooling drums is converted into a rapidly cooled solidified slag through heat exchange with a cooling medium passing through the plurality of cooling through-holes in the peripheral wall along with the rotation of each of the pair of cooling drums. The cooling medium supplied to the plurality of cooling through-holes in the peripheral wall of the pair of cooling drums 2 is heated by the molten slag 15 deposited on the peripheral surface of each of the pair of cooling drums 2. When the rapidly cooled solidified slag 15' reaches the lower half of each of the pair of cooling drums 2 along with the rotation of each of the pair of cooling drums 2, the rapidly cooled solidified slag 15' on the peripheral surfaces of the cooling drums 2 is peeled off therefrom, while being crushed by a scraper 16 supported on the housing 1 by means of a suitable supporting means (not shown), and drops into the lower part of the housing 1. A suitable opening and closing means not shown in provided in a discharging port 1b of the lower part of the housing 1. The peripheral surface of each of the pair of cooling drums 2 from which the rapidly cooled solidified slag 15' has been peeled off by the scraper 16 comes again into contact with the molten slag 15 in the slag sump 13 along with the rotation of each of the pair of cooling drums 2, whereby a rapidly cooled solidified slag is continuously manufactured.
According to the above-mentioned apparatus for manufacturing a rapidly cooled solidified slag, it is possible to continuously manufacture a rapidly cooled solidified slag which is free of water and excellent in crushability, and furthermore, to easily recover the heat contained in the molten slag from the cooling medium after heat exchange, since the molten slag deposited on the peripheral surfaces of the pair of cooling drums 2 is subjected to heat exchange with the cooling medium for cooling the pair of cooling drums 2. However, the above-mentioned apparatus for manufacturing a rapidly cooled solidified slag has the following problems:
(1) A rapidly cooled solidified slag may well be manufactured at a high productivity by using cooling drums having a large diameter and rotated at a large number of revolutions. For example, when employing a pair of cooling drums 2 having a diameter of 2,000 mm and a molten blast furnace slag as the molten slag, and rotating this pair of 2,000 mm diameter cooling drums at 3.0 r.p.m., the molten blast furnace slag is deposited into a thickness of from 3.8 to 4.0 mm on the peripheral surfaces of the pair of cooling drums. Along with the rottion of the pair of 2,000 mm diameter cooling drums 2, the molten blast furnace slag deposited on the peripheral surfaces thereof is rapidly cooled, solidified and peeled off therefrom while being crushed by the scraper 16, and is thus converted into a rapidly cooled solidified slag having a vitrification ratio of about 80%. However, the pair of 2,000 mm diameter cooling drums are rotated at revoltions of over 3.0 r.p.m., the thickness of the molten blast furnace slag deposited on the peripheral surfaces thereof becomes slightly larger in response to the increase of the revolutions. In this case, furthermore, the molten blast furnace slag deposited on the peripheral surfaces of the pair of 2,000 mm diameter cooling drums 2 is only partially vitrified, peeled off by the scraper 16 from the peripheral surfaces of the cooling drums 2 before substantial completion of the entire solidification, and drops into the lower part of the hopper 1. As a result, the blast furnace slag partially not as yet solidified which has dropped into the lower part of the hopper 1 is heated at the vitreous portions thereof by its own heat, and becomes thereafter a slow-cooled slag containing very little vitreous portions.
(2) If the thickness of the molten slag 15 deposited on the peripheral surfaces of the pair of cooling drums 2 is large, this impairs the efficiency of heat exchange between the molten slag deposited on the peripheral surfaces of the pair of cooling drums 2 and the cooling medium passing through the pair of cooling drums 2, because of the increased thickness of the heat conducting layer of the deposited slag. (3) The weirs 12 which are supported on the housing 1 are stationary. Therefore, long continuous supply of the molten slag 15 to the slag sump 13 causes the molten slag in the slag sump 13 to be deposited and solidified on the inner surfaces of the weirs 12. As a result, the solidified slag deposited on the inner surfaces of the weirs 12 prevents the molten slag 15 in the slag sump 13 from being deposited on the peripheral surfaces of the pair of cooling drums 2, and impairs smooth rotation of the pair of cooling drums 2.
(4) The weirs 12 are heated by the molten slag 15 in the slag sump 13. However, the weirs 12 are simply in contact with the both ends of the pair of cooling drums 2 so as to prevent the molten slag 15 in the slag sump 13 from flowing out therefrom. Therefore, the heat imparted to the weirs 12 by the molten slag 15 in the slag sump 13 cannot be recovered.